The present invention relates to electromechanical information storage systems.
It is well known in the field of magnetic information storage systems that a means for increasing storage density and signal resolution is to reduce the separation between a transducer and associated media. For many years, devices incorporating flexible media, such as floppy disk or tape drives, have employed a head in contact with the flexible media during operation in order to reduce the head-media spacing. Recently, hard disk drives have been designed which can durably operate with high-speed contact between the hard disk surface and the head.
A head for a hard disk drive typically includes microscopic solid layers formed on a ceramic or ferrite substrate, and can easily be damaged by such high-speed contact. Moreover, a head can also damage a disk during such contact, which may occur at speeds exceeding ten meters per second. In an attempt to prevent such damage, which can destroy a disk and the data stored thereon, hard disk media is conventionally coated with a carbon or carbon-based overcoat that is hard and durable. Similarly, a slider that carries a transducer for a disk drive head is usually formed of a hard durable material, such as alumina (Al2O3)/titanium-carbide (TiC), which is commonly referred to as AlTiC. Another suitable slider or disk material is silicon carbide (SiC), which may be sintered or formed by high-temperature chemical vapor deposition (CVD), as described in. U.S. Pat. No. 5,465,184 to Pickering et al.
Another means for increasing signal resolution that has become increasingly common is the use of magnetoresistive (MR) or other sensors for a head. MR elements may be used along with inductive writing elements, or may be separately employed as sensors. While MR sensors offer greater sensitivity than inductive transducers, they are even more prone to damage from high-speed contact with a hard disk surface, and may also suffer from corrosion. For these reasons, air bearing surfaces (ABS) for heads containing MR sensors are conventionally coated with a hard, durable carbon or carbon-based overcoat.
Current methods for making overcoats for slider or disk surfaces include sputtering or ion beam chemical vapor deposition (IBCVD) to form diamond-like carbon (DLC) films. More recently, cathodic arc deposition has been used to form tetrahedral-amorphous carbon (ta-C) films having even greater hardness. Employment of harder films allows the thickness of the films to be reduced, which can help to reduce head-media spacing.
DLC and ta-C films have a high stress as well as high hardness, and do not adhere well to slider ABS or magnetic layers, and so an adhesion layer of Si or Si3N4 is conventionally formed to help with stress relief and adhesion. FIG. 1 depicts such a conventional DLC coating 20 that has been formed on an interlayer 22 of Si or Si3N4, which in turn was formed on a substrate 25 that may be a magnetic or ceramic layer of a head. The DLC coating 20 conventionally has a thickness that is about four times that of the interlayer 22. Thus a 80 xc3x85 layer 20 of DLC may be formed on a 20 xc3x85 interlayer 22 of Si3N4, to create a minimum head spacing of 100 xc3x85, while a similar spacing may be present on the media. Further head-media spacing conventionally occurs due to penetration of energetic interlayer ions into underlying magnetic layers, deadening a portion of those magnetic layers.
It is not clear that the minimum head-medium spacing due to these layers can be reduced substantially without encountering problems in overcoat durability and interlayer continuity. For example, a 10 xc3x85 interlayer may be only a few atoms thick, and may not provide adequate adhesion even if one assumes that the somewhat thicker carbon overcoat can withstand high-speed head-disk contact without damage or removal.
The present invention provides a thinner overcoat for a head and/or media surface, substantially reducing head-media spacing and increasing areal storage density and resolution. The overcoat is hard and durable silicon-carbide (SiC), and does not require an interlayer to promote adhesion to underlying magnetic or ceramic layers.
The SiC is formed in a manner that creates an overcoat with density, hardness, durability and corrosion resistance similar to DLC. The SiC overcoat may also be formed with a process that penetrates less into an underlying magnetic layer than is conventional, reducing further the spacing of active elements by inactive coatings.
Alternatively, SiC may be formed by this process as an interlayer for a carbon overcoat such as DLC or ta-C. This allows the overcoat to be made thinner, since the interlayer is hard and dense, while retaining the chemical and other surface properties of the carbon overcoat.